It is often desirable to reinforce rubber articles by incorporating therein metal reinforcing elements. For example, tires, conveyor belts, power transmission belts, timing belts, hoses and a variety of other rubber articles are often reinforced with metal wire. In order for rubber articles which are provided with steel reinforcing elements to function effectively, it is important that good adhesion between the rubber and the metal reinforcing elements be maintained. One of the most common methods of enhancing the adhesion of wire filaments to rubber is to coat the filament with another material, for example, pneumatic vehicle tires are often reinforced with cords prepared from steel filaments which are coated with brass. Normally, steel reinforcing elements are coated with a brass that is an alloy of copper and zinc.
It is also known that various agents can be mixed into the rubber which will increase adhesion between the rubber and metal reinforcements embedded in it. U.S. Pat. No. 3,894,903 discloses a process for improving the bonding of rubber to copper and copper alloys by incorporating into the rubber before vulcanization certain triazines, for example 2-(3-hydroxyphenoxy)-4-chloro-6-aminotriazine.
Peroxide initiated curing systems for rubbery materials have proven to be unsatisfactory in the production of finished articles that are required to have extended flex life, for peroxide cured rubbers tend to crack when subject to repeated flexing. Additionally, peroxide curing systems tend to be expensive and because of their reactivity, they require careful handling to avoid the creation of a dangerous environment.
As a result, many industries, such as the tire and industrial belting industries prefer to use sulfur cure vulcanization systems for cross-linking rubber.